1. Field of the Invention
The present invention relates generally to data storage systems, and more particularly, to a data storage system comprising an air bearing slider assembly having a burnishing structure.
2. Background of the Related Art
A typical data storage system includes one or more data storage disks coaxially mounted on a hub of a spindle motor. The spindle motor rotates the disks at speeds typically on the order of several thousand revolutions-per-minute. Digital information, representing various types of data, is typically written to and read from the data storage disks by one or more transducers, or read/write heads, which are mounted to an actuator and passed over the surface of the rapidly rotating disks. The actuator typically includes one or more outwardly extending arms onto which one or more air bearing sliders are mounted at a distal end of the arms. One or more transducers, in turn, are disposed on the air bearing slider. Airflow produced above the disk surface by the rapidly rotating disks results in the production of an air bearing upon which the aerodynamic slider is supported, thus causing the slider to fly a small distance above the rotating disk surface.
The actuator arms are interleaved into and out of the stack of rotating disks, typically by means of a coil assembly mounted to the actuator. The coil assembly generally interacts with a permanent magnet structure, and the application of current to the coil in one polarity causes the actuator arms and sliders to shift in one radial direction, while current of the opposite polarity shifts the actuator arms and sliders in an opposite radial direction.
In a typical digital data storage system, digital data is stored in the form of magnetic transitions on a series of concentric, closely spaced tracks comprising the surface of the magnetizable rigid data storage disks. The tracks are generally divided into a plurality of sectors, with each sector comprising a number of information fields. One of the information fields is typically designated for storing data, while other fields contain sector identification and synchronization information, for example. Data is transferred to and retrieved from specified track and sector locations by the transducers being shifted from track to track, typically under the control of a controller. The transducer assembly typically includes a read element and a write element. Other transducer assembly configurations incorporate a single transducer element used to read and write data to and from the disks.
The transducer, also referred to as a read/write head, is one of the most important components in a magnetic disk drive system. A conventional read/write head operates by sensing the rate of change of magnetic flux transitions stored on the surface of a magnetic disk. The read/write head produces an electrical output signal in response to the sensed magnetic flux transitions. The read/write head""s output signal is velocity dependent, i.e., a faster disk speed yields a greater magnitude output signal.
Magneto-resistive (MR) read/write heads represent an important improvement in magnetic disk drive systems. The output signal of a MR head is not dependent on the relative velocity between the head and the disk. Instead of simply sensing a magnetic field from the disk surface, an MR head senses the rate of change of that field. MR heads may employ a similar write element as a conventional head. However, a MR head uses a modified read element employing features such as a thin sensing element called an xe2x80x9cMR stripexe2x80x9d. The MR stripe operates based upon the magnetoresistive effect. Namely, the resistance of the MR stripe changes in proportion to the magnetic field of the disk, passing by the MR stripe. If the MR stripe is driven with a constant current, the MR stripe""s voltage drop is proportional to its resistance. Thus, the MR stripe""s voltage represents the magnetic signals encoded on the disk surface. In other arrangements, a constant voltage is applied to the MR stripe, and the resultant current is measured to detect magnetic signals stored on the disk surface.
Although highly beneficial, MR heads are especially susceptible to certain errors. Namely, the resistance of the MR stripe varies in response to heating and cooling of the MR stripe, in addition to the magnetic flux signals encoded on the disk surface. Normally, the MR stripe maintains a constant temperature as the slider flies over the disk surface, separated by a thin cushion of air created by the rapidly spinning disk. In this state, the stored magnetic flux signals contribute most significantly to the MR stripe""s output signals, as intended. An MR stripe, however, may experience heating under certain conditions, especially when the MR head inadvertently contacts another object.
Contact with the MR head may occur in a number of different ways. For instance, the MR head may contact a raised irregularity in the disk surface, such as a defect in the material of the disk surface or a contaminant such as a particle of dust, debris, etc. Also, the MR head may contact the disk surface during a high shock event, where G-forces momentarily bounce the MR head against the disk surface.
Such contact results in heating of the MR head, including the MR stripe. Heating of the MR stripe increases the stripe resistance, which distorts the MR stripe""s output signal. This type of distortion is known in the art as a xe2x80x9cthermal asperity.xe2x80x9d A read channel in a magnetic disk drive, however, requires a reliable signal from the MR head, free from irregularities such as thermal asperities. Consequently, severe thermal asperities may prevent the read channel from correctly processing output signals of the MR head, causing a channel error.
These errors may be manifested in a number of different ways. For instance, severe distortions of the channel signal may cause the magnetic disk drive to shut down. Other errors may simply prevent reading of data on the disk. Such errors may also prevent writing of data, if the servo signal embedded in the disk cannot be read correctly, or it indicates that the head is too far off track to write data without overwriting data on an adjacent track. This condition is called a xe2x80x9cwrite inhibit errorxe2x80x9d. If errors of this type persist, the disk drive may deem the entire sector xe2x80x9cbadxe2x80x9d, causing a write inhibit xe2x80x9chardxe2x80x9d error. Repeated thermal asperities may also cause a disk drive to fail a predictive failure analysis measure, falsely signaling an impending disk failure to the disk drive user. As shown by the foregoing, thermal asperities in magnetic disk drive systems may cause significant problems in disk drives that use MR heads.
Therefore, there exists a need for a data storage system capable of removing disk surface irregularities and/or contaminant particles on disk surfaces that may cause thermal asperities in the transducer output. It would be desirable for the data storage system to provide selective in-situ operation between a normal read/write operation and a disk surface burnishing operation.
A data storage system capable of removing disk surface irregularities and/or contaminant particles on disk surfaces that may cause thermal asperities in the transducer output is provided. The data storage system provides selective in-situ operation between a normal read/write operation and a disk surface burnishing operation.
One embodiment provides a data storage system, comprising: a data storage disk; a rotating actuator disposed to rotate the data storage disk; a suspension arm movably disposed above the data storage disk; an actuator disposed to move the suspension arm; and an air bearing slider assembly pivotally attached to the suspension arm, the air bearing slider assembly comprising: a slider having an air bearing surface; a transducer disposed in a distal portion of the slider; a burnishing element disposed on the air bearing surface; and a pitch angle control assembly disposed in connection with the slider to control a pitch angle of the air bearing surface.
Another embodiment provides an air bearing slider assembly, comprising: a slider having an air bearing surface; a burnishing element disposed on the air bearing surface; a pivot mount disposed on the slider adapted for pivotally mounting the slider to a suspension arm; and a pitch angle control assembly disposed in connection with the slider to control a pitch angle of the air bearing surface, wherein the pitch angle control assembly comprises a first magnet disposed on an upper surface of the slider; and an electromagnet disposed on the suspension arm to provide a repelling magnetic force against the first magnet, the electromagnet adapted for connection with a controller for controlling the repelling magnetic force.
Another embodiment provides an air bearing slider assembly, comprising: a slider having an air bearing surface; a burnishing element disposed on the air bearing surface; a pivot mount disposed on the slider adapted for pivotally mounting the slider to a suspension arm; and a pitch angle control assembly disposed in connection with the slider to control a pitch angle of the air bearing surface, wherein the pitch angle control assembly comprises a pitch angle control tab disposed on the slider, extending from the slider through a slot in the suspension arm, a first magnet disposed on a lower surface of the pitch angle control tab, and an electromagnet disposed on an upper surface of the suspension arm to provide a repelling magnetic force against the first magnet, the electromagnet adapted for connection with a controller for controlling the repelling magnetic force.
Another embodiment provides a method for removing surface irregularities on a disk surface comprising selectively controlling a pitch angle of an air bearing surface of a slider between a normal position and a burnishing position, the air bearing surface having a transducer and one or more burnishing elements disposed thereon.
Another embodiment provides a method for removing surface irregularities on a disk surface comprising selectively controlling a pitch angle of an air bearing surface of a slider between a normal position and a burnishing position, the air bearing surface having a transducer and one or more burnishing elements disposed thereon, and monitoring the disk surface to determine whether a burnishing operation needs to be repeated.